The invention relates to the sector of braking control circuits for all types of vehicle, particularly automobiles and motorcycles.
As stated, the invention has particularly advantageous applications in the hydraulic braking circuits of vehicles where force must be applied to an actuating component such as a handle or pedal to deliver pressure capable of acting on the braking components. This type of application must not, however, be considered as strictly limitative.
It is known by those skilled in the art that braking components, particularly calipers, are fitted with pads controlled by pistons that are hydraulically linked to a master cylinder controlled by one or more actuating components that can be moved with the hand or foot depending on the type of vehicle concerned. It is also known that the act of braking, which consists of a deceleration, causes the transfer of mass to the front of the vehicle such that there tends to be loss of weight at the rear of the vehicle that is capable of causing breakaway such as that found in motorcycles.
FIG. 1 shows the iso-adhesion curve of an ideal theoretical braking as a function of the pressure exerted on the front wheel or wheels (Y-axis) relative to the pressure exerted on the back wheel or wheels (X-axis). This curve shows that there is a rise in pressure in the braking components of the back wheel or wheels which is followed by a progressive drop as pressure is released in the said braking components.
In actual fact, when the user uses the actuating components there is a rise in pressure that results in the theoretical curve being exceeded, resulting in one or more of the back wheels locking.
To attempt to overcome these drawbacks, pressure limiters have been proposed for inclusion in the control circuits of the braking components of the rear wheel or wheels, the primary function of which is to limit the rise in pressure but which do not cause it to drop progressively. At best such pressure limiters make it possible to maintain this pressure at a constant level on a plateau that appears at the maximum of the theoretical curve. Moreover, such limiters are sensitive to the speed at which pressure rises. There is therefore significant dispersion of the set pressure according to the speed at which pressure rises in the circuit.